OK - this makes sense to a point - however the point of highest potential is at the CHARGER, not the battery - otherwise, it would never charge the batteries! Maybe a charger lead should have a fuse at both ends???
- - The word "Potential" is used in electric circuits to mean "voltage". It is the "amperes" that cause the heating problem (in combination with volts to make watts.) It would be extremely rare and IMHO virtually impossible for a battery charger to output an over-voltage significant enough to affect the wire safety. You can run many Kilovolts down a hair thin wire so long as the amperes are kept extremely low. TV CRT's (old fashioned tube-TV's) had several kilo-volts delivered to them in rather small size wires.
- - For instance during the starting of your engine, up to a thousand amperes race down your starting cable at 10 to 12 volts. Only because the time factor is a few seconds or less does the cable not catch on fire. Fuses and C/B's are rated to blow/trip only after a preset amount of time. Excessive amps through a C/B start a heating process that will "trip" it when sufficient heat is generated. After tripping you have to wait for the element inside to cool before you can reset the C/B.
- - The real threat to your wires - reference a battery charger - is the shorting of a component in the battery charger that would allow excessive amperage to flow from the "well/big supply" held in the batteries through the wires to the battery charger causing the wires to heat up and catch fire.
- - There are internal fuses inside the battery charger that will blow if you attempt to "suck" more power out of the battery charger than it is rated to supply. This would happen if there was an internal short in a battery or a dead short at the output of the battery charger. These protections have been in place for a very long time. What wasn't done previously was protect the wires from the battery supply end as it was considered highly unlikely that something could cause a dead short up inside the battery charger.
- - All the connections used to be up inside a compartment of the battery charger - now they are external to the battery charger case and some stray piece of metal could physically fall across the gap between ground and hot terminals causing the dead short.